1. Field of the Invention
The invention relates to a method of manufacturing metallic components consisting of at least two different materials, one of them being an iron-based alloy and the other an aluminum-based alloy. More particularly, the present invention relates to a method of manufacturing metallic components including the steps of depositing a metallic layer onto a body made from the iron-based alloy, the layer being an aluminum-based alloy, preferably based on Al—Si or Fe, and placing the body in a casting mold and casting an aluminum-based alloy about the body.
2. Description of the Related Art
In order to meet both the tribological and the manufacturing requirements on internal combustion engines, and more specifically those placed on the system piston, piston ring and cylinder liner, wear-resistant bodies are cast in the engine block. Depending on the load, various materials may be combined. For reasons of weight, ease of production and specific properties, aluminum alloys are used for engine blocks. In those regions of the system piston, piston ring and cylinder liner that are subject to tribological conditions, by contrast, iron-base alloys are used. For example, the cylinder liner being cast in the engine block and the ring bearing are manufactured from iron-based alloys. Due to the different specific properties of the materials, establishing a mechanical or metallurgical bond between the materials has always been a problem. Both the dynamic and the thermal properties in the internal combustion engine place high demands on the bond.
The “Alfin” process described in DE 95 86 14 has long been known as a method of achieving a metallurgical bond between different alloys. In this process, an aluminum alloy, of a few hundredth of millimeters thick, is deposited onto an iron-containing cylinder liner, thus providing a connection by diffusive bonding. As the cylinder liner is cast-in, the casting material is bonded to the diffusion layer.
To increase the metallurgical bond between the iron-containing part and the aluminum layer deposited, the document DE 23 44 899 suggests depositing a flux onto the iron-containing core. Although this measure may promote diffusive bonding with the iron-containing core, it has no effect on the casting-in.
A problem with the bond between the layer created by the “Alfin” process and the cast-in aluminum alloy is that an oxide layer forms on the aluminum. The oxide layers of the aluminum have a very high melting point of about 2000° C., while most current aluminum alloys having melting temperatures below 1000° C.
In responding to this problem and to the aforementioned ones, DE 43 25 864 A1 suggests a method in which a layer of chromium is electroplated over the aluminum layer. Although a bond achieved, this method is susceptible to a greater number of barrier layers in which pores and bonding failures may arise. Another drawback is that an oxide layer forms on the layer of chromium which makes wetting more difficult.
It is the object of the present invention to overcome the drawbacks of prior art and to enhance the metallurgical bond between the components made from various materials.